A code division multiple access (CDMA) system is widely applied because of its advantages such as high capacity, high service quality, and good confidentiality. Because the CDMA system differentiates a user according to a feature code, in a mobile communication environment, a problem of multiple access interference (MAI) exists. However, in the CDMA system, a problem of near-far interference exists, that is, because distances between users and a base station or fading depths of user signals are different, a strong signal suppresses a weak signal, so that a weak user signal cannot be normally detected. Currently, user signal detection may be classified into a single-user detection technology and a multi-user detection technology. Interference cancellation is widely applied as a multi-user detection technology. An interference cancellation system in the prior art is adverse to improvement of a gain of a user signal after interference cancellation.